Lightroom doesn't use the Camera Raw plug-in. All of the Camera Raw technology is part of the Lightroom program. It will be necessary for you to wait for the next Lightroom update to have support for the NEF files from your camera. There is a DNG converter 8.7 RC (release candidate) that will support converting your NEF files to DNG format. Those files can be opened in Lightroom 5.6. When the next Lightroom update is released you can discontinue using the DNG converter if you so choose.